Bulk acoustic wave resonator filters including rejection-band resonators

ABSTRACT

A BAW resonator filter can include a BAW resonator pass-band filter ladder, the BAW resonator pass-band filter ladder can be configured to pass frequency components of an input signal in a pass-band of frequencies received at an input node of the BAW resonator pass-band filter ladder to an output node of the BAW resonator pass-band filter ladder. A first rejection-band series resonator can be coupled in series between an input port of the BAW resonator pass-band filter ladder and the input node, the first rejection-band series resonator can have a first anti-resonant frequency peak in a rejection-band of frequencies that is less than the pass-band of frequencies. A second rejection-band series resonator can be coupled in series between an output port of the BAW resonator filter and the output node, the second rejection-band series resonator can have a second anti-resonant frequency peak in the rejection-band of frequencies.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/660,227; entitled “BULK ACOUSTIC WAVE RESONATOR FILTERSINCLUDING REJECTION-BAND RESONATORS” filed Oct. 22, 2019 which claimspriority to U.S. Provisional Application Ser. No. 62/845,009 entitled“WiFi 5 GHz NEW APPROACH FOR REJECTION IMPROVEMENT,” filed in theU.S.P.T.O. on May 8, 2019 and to U.S. Provisional Application Ser. No.62/885,047 entitled “BULK ACOUSTIC WAVE RESONATOR FILTERS INCLUDINGREJECTION-BAND RESONATORS,” filed in the U.S.P.T.O. on Aug. 9, 2019, andis a continuation-in-part application of U.S. patent application Ser.No. 16/135,276, titled “FRONT END MODULE FOR 5.2 GHZ WI-FI ACOUSTIC WAVERESONATOR RF FILTER CIRCUIT,” filed Sep. 19, 2018, which is acontinuation-in-part application of U.S. patent application Ser. No.16/019,267, titled “5.2 GHz Wi-Fi ACOUSTIC WAVE RESONATOR RF FILTERCIRCUIT,” filed Jun. 26, 2018, which is a continuation-in-partapplication of U.S. patent application Ser. No. 15/784,919, titled“PIEZOELECTRIC ACOUSTIC RESONATOR MANUFACTURED WITH PIEZOELECTRIC THINFILM TRANSFER PROCESS,” filed Oct. 16, 2017, which is acontinuation-in-part of U.S. application Ser. No. 15/068,510 filed Mar.11, 2016.

The present application incorporates by reference, for all purposes, thefollowing concurrently filed patent applications, all commonly owned:U.S. patent application Ser. No. 14/298,057, titled “RESONANCE CIRCUITWITH A SINGLE CRYSTAL CAPACITOR DIELECTRIC MATERIAL”, filed Jun. 6, 2014(now U.S. Pat. No. 9,673,384 issued Jun. 6, 2017); U.S. patentapplication Ser. No. 14/298,076, titled “METHOD OF MANUFACTURE FORSINGLE CRYSTAL CAPACITOR DIELECTRIC FOR A RESONANCE CIRCUIT”, filed Jun.6, 2014 (now U.S. Pat. No. 9,537,465 issued Jan. 3, 2017); U.S. patentapplication Ser. No. 14/298,100, titled “INTEGRATED CIRCUIT CONFIGUREDWITH TWO OR MORE SINGLE CRYSTAL ACOUSTIC RESONATOR DEVICES”, filed Jun.6, 2014 (now U.S. Pat. No. 9,571,061 issued Feb. 14, 2017); U.S. patentapplication Ser. No. 14/341,314, titled “WAFER SCALE PACKAGING”, filedJul. 25, 2014 (now U.S. Pat. No. 9,805,966 issued Oct. 31, 2017); U.S.patent application Ser. No. 14/449,001, titled “MOBILE COMMUNICATIONDEVICE CONFIGURED WITH A SINGLE CRYSTAL PIEZO RESONATOR STRUCTURE”,filed Jul. 31, 2014 (now U.S. Pat. No. 9,716,581 issued Jul. 25, 2017);U.S. patent application Ser. No. 14/469,503, titled “MEMBRANE SUBSTRATESTRUCTURE FOR SINGLE CRYSTAL ACOUSTIC RESONATOR DEVICE”, filed Aug. 26,2014 (now U.S. Pat. No. 9,917,568 issued Mar. 13, 2018). The disclosuresof all of the above applications and patents are incorporated herein byreference.

BACKGROUND

The present invention relates generally to electronic devices. Moreparticularly, the present invention provides techniques related to amethod of manufacture and a structure for bulk acoustic wave resonatordevices, single crystal bulk acoustic wave resonator devices, singlecrystal filter and resonator devices, and the like. Merely by way ofexample, the invention has been applied to a single crystal resonatordevice for a communication device, mobile device, computing device,among others.

Mobile telecommunication devices have been successfully deployedworld-wide. Over a billion mobile devices, including cell phones andsmartphones, were manufactured in a single year and unit volumecontinues to increase year-over-year. With ramp of 4G/LTE in about 2012,and explosion of mobile data traffic, data rich content is driving thegrowth of the smartphone segment—which is expected to reach 2B per annumwithin the next few years. Coexistence of new and legacy standards andthirst for higher data rate requirements is driving RF complexity insmartphones. Unfortunately, limitations exist with conventional RFtechnology that is problematic, and may lead to drawbacks in the future.

With 4G LTE and 5G growing more popular by the day, wireless datacommunication demands high performance RF filters with frequenciesaround 5 GHz and higher. Bulk acoustic wave resonators (BAWR) usingcrystalline piezoelectric thin films are leading candidates for meetingsuch demands. Current BAWRs using polycrystalline piezoelectric thinfilms are adequate for bulk acoustic wave (BAW) filters operating atfrequencies ranging from 1 to 3 GHz; however, the quality of thepolycrystalline piezoelectric films degrades quickly as the thicknessesdecrease below around 0.5 um, which is required for resonators andfilters operating at frequencies around 5 GHz and above. Singlecrystalline or epitaxial piezoelectric thin films grown on compatiblecrystalline substrates exhibit good crystalline quality and highpiezoelectric performance even down to very thin thicknesses, e.g., 0.4um. Even so, there are challenges to using and transferring singlecrystal piezoelectric thin films in the manufacture of BAWR and BAWfilters.

SUMMARY

Embodiments according to the invention can provide bulk acoustic waveresonator filters including rejection-band resonators. Pursuant to theseembodiments, in some embodiments according to the invention, a BulkAcoustic Wave (BAW) resonator filter can include a BAW resonatorpass-band filter circuit, the BAW resonator pass-band filter circuitconfigured to pass frequency components of an input signal in apass-band of frequencies received at an input node of the BAW resonatorpass-band filter circuit to an output node of the BAW resonatorpass-band filter circuit. A first rejection-band series resonator can becoupled in series between an input port of the BAW resonator pass-bandfilter circuit and the input node, the first rejection-band seriesresonator having a first anti-resonant frequency peak in arejection-band of frequencies that is less than the pass-band offrequencies. A second rejection-band series resonator can be coupled inseries between an output port of the BAW resonator filter and the outputnode, the second rejection-band series resonator having a secondanti-resonant frequency peak in the rejection-band of frequencies.

In some embodiments according to the invention, a Bulk Acoustic Wave(BAW) resonator filter can include a BAW resonator pass-band filtercircuit, the BAW resonator pass-band filter circuit configured to passfrequency components of an input signal in a pass-band of frequenciesreceived at an input port of the BAW resonator pass-band filter circuitto an output port of the BAW resonator pass-band filter circuit. A firstrejection-band shunt resonator can be coupled in parallel across aninput port of the BAW resonator pass-band filter circuit and a referencenode of the BAW resonator pass-band filter circuit, the firstrejection-band shunt resonator having a first resonant frequency peak ina rejection-band of frequencies that is greater than the pass-band offrequencies. A second rejection-band shunt resonator can be coupled inparallel between the output port of the BAW resonator filter and thereference node, the second rejection-band shunt resonator having asecond resonant frequency peak in the rejection-band of frequencies.

In some embodiments according to the invention, a Bulk Acoustic Wave(BAW) resonator filter can include a BAW resonator pass-band filtercircuit, the BAW resonator pass-band filter circuit configured to passfrequency components of an input signal in a pass-band of frequenciesreceived at an input node of the BAW resonator pass-band filter circuitto an output node of the BAW resonator pass-band filter circuit. A firstrejection-band series resonator can be coupled in series with an inputport of the BAW resonator pass-band filter circuit or an output port ofthe BAW resonator pass-band filter circuit, the first rejection-bandseries resonator having a first anti-resonant frequency peak in arejection-band of frequencies that is less than the pass-band offrequencies.

In some embodiments according to the invention, a Bulk Acoustic Wave(BAW) resonator filter can include a BAW resonator pass-band filtercircuit configured to pass frequency components of an input signal in apass-band of frequencies received at an input port of the BAW resonatorpass-band filter circuit to an output port of the BAW resonatorpass-band filter circuit. A first rejection-band shunt resonator can becoupled in parallel across an input port of the BAW resonator pass-bandfilter circuit and a reference node of the BAW resonator pass-bandfilter circuit or coupled in parallel between the output port of the BAWresonator filter and the reference node, the first rejection-band shuntresonator having a first resonant frequency peak in a rejection-band offrequencies that is greater than the pass-band of frequencies.

In some embodiments according to the invention, a Bulk Acoustic Wave(BAW) resonator filter can include a first BAW resonator pass-bandfilter circuit configured to pass frequency components of an inputsignal in a first pass-band of frequencies received at an input port ofthe first BAW resonator pass-band filter circuit to an output port ofthe first BAW resonator pass-band filter circuit. A first rejection-bandseries resonator can be coupled in series with the input port of the BAWresonator pass-band filter circuit or the output port of the BAWresonator pass-band filter circuit, the first rejection-band seriesresonator having a first anti-resonant frequency peak in a firstrejection-band of frequencies that is less than the first pass-band offrequencies. A second BAW resonator pass-band filter circuit can beconfigured to pass frequency components of the input signal in a secondpass-band of frequencies received at the input port of the second BAWresonator pass-band filter circuit to the output port of the second BAWresonator pass-band filter circuit. A first rejection-band shuntresonator cane be coupled in parallel across the input port of thesecond BAW resonator pass-band filter circuit and a reference node ofthe second BAW resonator pass-band filter circuit or coupled in parallelbetween the output port of the second BAW resonator filter and thereference node, the first rejection-band shunt resonator having a firstresonant frequency peak in a second rejection-band of frequencies thatis greater than the second pass-band of frequencies. A switch can beconfigured to couple the input signal to the first rejection-band seriesresonator in a first state and configured to couple the input signal tothe first rejection-band shunt resonator in a second state.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings in which:

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice having topside interconnections according to an example of thepresent invention.

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice having bottom-side interconnections according to an example ofthe present invention.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention.

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 4A is a simplified diagram illustrating a step for a methodcreating a topside micro-trench according to an example of the presentinvention.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step of forming a topside micro-trench asdescribed in FIG. 4A.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step of forming a topside micro-trenchas described in FIG. 4A.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 9A is a simplified diagram illustrating a method step for formingbackside trenches according to an example of the present invention.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step of forming backside trenches, asdescribed in FIG. 9A, and simultaneously singulating a seed substrateaccording to an embodiment of the present invention.

FIG. 10 is a simplified diagram illustrating a method step formingbackside metallization and electrical interconnections between top andbottom sides of a resonator according to an example of the presentinvention.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device using a blind viainterposer according to an example of the present invention.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIGS. 14A to 14G are simplified diagrams illustrating method steps for acap wafer process for an acoustic resonator device according to anexample of the present invention.

FIGS. 15A-15E are simplified diagrams illustrating method steps formaking an acoustic resonator device with shared backside trench, whichcan be implemented in both interposer/cap and interposer free versions,according to examples of the present invention.

FIGS. 16A-16C through FIGS. 31A-31C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a transfer process using a sacrificiallayer for single crystal acoustic resonator devices according to anexample of the present invention.

FIGS. 32A-32C through FIGS. 46A-46C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a cavity bond transfer process for singlecrystal acoustic resonator devices according to an example of thepresent invention.

FIGS. 47A-47C though FIGS. 59A-59C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a solidly mounted transfer process forsingle crystal acoustic resonator devices according to an example of thepresent invention.

FIG. 60 is a simplified diagram illustrating filter pass-bandrequirements in a radio frequency spectrum according to an example ofthe present invention.

FIG. 61 is a simplified diagram illustrating an overview of key marketsthat are applications for acoustic wave RF filters according to anexample of the present invention.

FIG. 62 is a simplified diagram illustrating application areas for 5.2GHz RF filters in Tri-Band Wi-Fi radios according to examples of thepresent invention.

FIGS. 63A-63C are simplified diagrams illustrating cross-sectional viewsof resonator devices according to various examples of the presentinvention.

FIGS. 64A-64C are simplified circuit diagrams illustratingrepresentative lattice and ladder configurations for acoustic filterdesigns according to examples of the present invention.

FIGS. 65A-65B are simplified diagrams illustrating packing approachesaccording to various examples of the present invention.

FIG. 66 is a simplified diagram illustrating a packing approachaccording to an example of the present invention.

FIG. 67 is a simplified circuit diagram illustrating a 2-port BAW RFfilter circuit according to an example of the present invention.

FIG. 68 is a simplified table of filter parameters according to anexample of the present invention.

FIG. 69 is a simplified graph representing insertion loss over frequencyaccording to an example of the present invention.

FIGS. 70-74 is a simplified circuit block diagram illustrating a frontend module according to various examples of the present invention.

FIG. 75 is a schematic illustration of a BAW resonator filter includinga BAW resonator pass-band filter ladder and first and secondrejection-band series resonators in some embodiments according to theinvention.

FIG. 76 is a graph illustrating anti-resonant frequencies of first andsecond rejection-band series resonators in the BAW resonator filter ofFIG. 75 in some embodiments according to the invention.

FIG. 77 is a schematic illustration of a BAW resonator filter includinga BAW resonator pass-band filter ladder and first and secondrejection-band shunt resonators in some embodiments according to theinvention.

FIG. 78 is a graph illustrating resonant frequencies of first and secondrejection-band shunt resonators in the BAW resonator filter of FIG. 77in some embodiments according to the invention.

FIG. 79 is a schematic illustration of a combined BAW resonator filterincluding a BAW resonator pass-band filter ladder with first and secondrejection-band series resonators and a BAW resonator pass-band filterladder with first and second rejection-band shunt resonators controlledby a switch in some embodiments according to the invention.

FIG. 80 is a schematic illustration of a BAW resonator filter includinga BAW resonator pass-band filter lattice of FIG. 64A including first andsecond rejection-band series resonators in some embodiments according tothe invention.

FIG. 81 is a schematic illustration of a BAW resonator filter includinga BAW resonator pass-band filter lattice of FIG. 64B including first andsecond rejection-band series resonators in some embodiments according tothe invention.

FIG. 82 is a graph representative of the BAW resonator filter responseof FIGS. 80 and 81 including the anti-resonant frequencies of the firstand second rejection-band series resonators in some embodimentsaccording to the invention.

FIG. 83 is a schematic illustration of a BAW resonator filter includinga BAW resonator pass-band filter lattice of FIG. 64A including first andsecond rejection-band shunt resonators in some embodiments according tothe invention.

FIG. 84 is a schematic illustration of a BAW resonator filter includinga BAW resonator pass-band filter lattice of FIG. 64B including first andsecond rejection-band shunt resonators in some embodiments according tothe invention.

FIG. 85 is a graph representative of the BAW resonator filter responseof FIGS. 83 and 84 including the anti-resonant frequencies of the firstand second rejection-band shunt resonators in some embodiments accordingto the invention.

DETAILED DESCRIPTION OF EMBODIMENTS ACCORDING TO THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a method of manufacture andstructure for bulk acoustic wave resonator devices, single crystalresonator devices, single crystal filter and resonator devices, and thelike. Merely by way of example, the invention has been applied to asingle crystal resonator device for a communication device, mobiledevice, computing device, among others.

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice 101 having topside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying single crystal piezoelectric layer 120,which has a micro-via 129. The micro-via 129 can include a topsidemicro-trench 121, a topside metal plug 146, a backside trench 114, and abackside metal plug 147. Although device 101 is depicted with a singlemicro-via 129, device 101 may have multiple micro-vias. A topside metalelectrode 130 is formed overlying the piezoelectric layer 120. A top capstructure is bonded to the piezoelectric layer 120. This top capstructure includes an interposer substrate 119 with one or morethrough-vias 151 that are connected to one or more top bond pads 143,one or more bond pads 144, and topside metal 145 with topside metal plug146. Solder balls 170 are electrically coupled to the one or more topbond pads 143.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. The backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal plug147 is electrically coupled to the topside metal plug 146 and thebackside metal electrode 131. A backside cap structure 161 is bonded tothe thinned seed substrate 112, underlying the first and second backsidetrenches 113, 114. Further details relating to the method of manufactureof this device will be discussed starting from FIG. 2.

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice 102 having backside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying piezoelectric layer 120, which has amicro-via 129. The micro-via 129 can include a topside micro-trench 121,a topside metal plug 146, a backside trench 114, and a backside metalplug 147. Although device 102 is depicted with a single micro-via 129,device 102 may have multiple micro-vias. A topside metal electrode 130is formed overlying the piezoelectric layer 120. A top cap structure isbonded to the piezoelectric layer 120. This top cap structure 119includes bond pads which are connected to one or more bond pads 144 andtopside metal 145 on piezoelectric layer 120. The topside metal 145includes a topside metal plug 146.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. A backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal plug 146. This backside metalplug 147 is electrically coupled to the topside metal plug 146. Abackside cap structure 162 is bonded to the thinned seed substrate 112,underlying the first and second backside trenches. One or more backsidebond pads (171, 172, 173) are formed within one or more portions of thebackside cap structure 162. Solder balls 170 are electrically coupled tothe one or more backside bond pads 171-173. Further details relating tothe method of manufacture of this device will be discussed starting fromFIG. 14A.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention. As shown, device 103 includes athinned seed substrate 112 with an overlying single crystalpiezoelectric layer 120, which has a micro-via 129. The micro-via 129can include a topside micro-trench 121, a topside metal plug 146, abackside trench 114, and a backside metal plug 147. Although device 103is depicted with a single micro-via 129, device 103 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has the first andsecond backside trenches 113, 114. A backside metal electrode 131 isformed underlying a portion of the thinned seed substrate 112, the firstbackside trench 113, and the topside metal electrode 130. A backsidemetal plug 147 is formed underlying a portion of the thinned seedsubstrate 112, the second backside trench 114, and the topside metal145. This backside metal plug 147 is electrically coupled to the topsidemetal plug 146 and the backside metal electrode 131. Further detailsrelating to the method of manufacture of this device will be discussedstarting from FIG. 2.

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.As shown, device 104 includes a thinned seed substrate 112 with anoverlying single crystal piezoelectric layer 120, which has a micro-via129. The micro-via 129 can include a topside micro-trench 121, a topsidemetal plug 146, and a backside metal 147. Although device 104 isdepicted with a single micro-via 129, device 104 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has a first backsidetrench 113. A backside metal electrode 131 is formed underlying aportion of the thinned seed substrate 112, the first backside trench113, and the topside metal electrode 130. A backside metal 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal 147is electrically coupled to the topside metal plug 146 and the backsidemetal electrode 131. Further details relating to the method ofmanufacture of this device will be discussed starting from FIG. 2.

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1A. FIG. 2 can represent a method step of providing a partiallyprocessed piezoelectric substrate. As shown, device 102 includes a seedsubstrate 110 with a piezoelectric layer 120 formed overlying. In aspecific example, the seed substrate can include silicon, siliconcarbide, aluminum oxide, or single crystal aluminum gallium nitridematerials, or the like. The piezoelectric layer 120 can include apiezoelectric single crystal layer or a thin film piezoelectric singlecrystal layer.

FIG. 3 can represent a method step of forming a top side metallizationor top resonator metal electrode 130. In a specific example, the topsidemetal electrode 130 can include a molybdenum, aluminum, ruthenium, ortitanium material, or the like and combinations thereof. This layer canbe deposited and patterned on top of the piezoelectric layer by alift-off process, a wet etching process, a dry etching process, a metalprinting process, a metal laminating process, or the like. The lift-offprocess can include a sequential process of lithographic patterning,metal deposition, and lift-off steps to produce the topside metal layer.The wet/dry etching processes can includes sequential processes of metaldeposition, lithographic patterning, metal deposition, and metal etchingsteps to produce the topside metal layer. Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

FIG. 4A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 401 according to an exampleof the present invention. This figure can represent a method step offorming one or more topside micro-trenches 121 within a portion of thepiezoelectric layer 120. This topside micro-trench 121 can serve as themain interconnect junction between the top and bottom sides of theacoustic membrane, which will be developed in later method steps. In anexample, the topside micro-trench 121 is extends all the way through thepiezoelectric layer 120 and stops in the seed substrate 110. Thistopside micro-trench 121 can be formed through a dry etching process, alaser drilling process, or the like. FIGS. 4B and 4C describe theseoptions in more detail.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step as described in FIG. 4A. As shown, FIG.4B represents a method step of using a laser drill, which can quicklyand accurately form the topside micro-trench 121 in the piezoelectriclayer 120. In an example, the laser drill can be used to form nominal 50um holes, or holes between 10 um and 500 um in diameter, through thepiezoelectric layer 120 and stop in the seed substrate 110 below theinterface between layers 120 and 110. A protective layer 122 can beformed overlying the piezoelectric layer 120 and the topside metalelectrode 130. This protective layer 122 can serve to protect the devicefrom laser debris and to provide a mask for the etching of the topsidemicro-via 121. In a specific example, the laser drill can be an 11 Whigh power diode-pumped UV laser, or the like. This mask 122 can besubsequently removed before proceeding to other steps. The mask may alsobe omitted from the laser drilling process, and air flow can be used toremove laser debris.

FIG. 4C can represent a method step of using a dry etching process toform the topside micro-trench 121 in the piezoelectric layer 120. Asshown, a lithographic masking layer 123 can be forming overlying thepiezoelectric layer 120 and the topside metal electrode 130. The topsidemicro-trench 121 can be formed by exposure to plasma, or the like.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 4A. Thesefigures can represent the method step of manufacturing multiple acousticresonator devices simultaneously. In FIG. 4D, two devices are shown onDie #1 and Die #2, respectively. FIG. 4E shows the process of forming amicro-via 121 on each of these dies while also etching a scribe line 124or dicing line. In an example, the etching of the scribe line 124singulates and relieves stress in the piezoelectric single crystal layer120.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. FIG. 5 can represent the method step of formingone or more bond pads 140 and forming a topside metal 141 electricallycoupled to at least one of the bond pads 140. The topside metal 141 caninclude a topside metal plug 146 formed within the topside micro-trench121. In a specific example, the topside metal plug 146 fills the topsidemicro-trench 121 to form a topside portion of a micro-via.

In an example, the bond pads 140 and the topside metal 141 can include agold material or other interconnect metal material depending upon theapplication of the device. These metal materials can be formed by alift-off process, a wet etching process, a dry etching process, ascreen-printing process, an electroplating process, a metal printingprocess, or the like. In a specific example, the deposited metalmaterials can also serve as bond pads for a cap structure, which will bedescribed below.

FIG. 6 can represent a method step for preparing the acoustic resonatordevice for bonding, which can be a hermetic bonding. As shown, a top capstructure is positioned above the partially processed acoustic resonatordevice as described in the previous figures. The top cap structure canbe formed using an interposer substrate 119 in two configurations: fullyprocessed interposer version 601 (through glass via) and partiallyprocessed interposer version 602 (blind via version). In the 601version, the interposer substrate 119 includes through-via structures151 that extend through the interposer substrate 119 and areelectrically coupled to bottom bond pads 142 and top bond pads 143. Inthe 602 version, the interposer substrate 119 includes blind viastructures 152 that only extend through a portion of the interposersubstrate 119 from the bottom side. These blind via structures 152 arealso electrically coupled to bottom bond pads 142. In a specificexample, the interposer substrate can include a silicon, glass,smart-glass, or other like material.

FIG. 7 can represent a method step of bonding the top cap structure tothe partially processed acoustic resonator device. As shown, theinterposer substrate 119 is bonded to the piezoelectric layer by thebond pads (140, 142) and the topside metal 141, which are now denoted asbond pad 144 and topside metal 145. This bonding process can be doneusing a compression bond method or the like. FIG. 8 can represent amethod step of thinning the seed substrate 110, which is now denoted asthinned seed substrate 111. This substrate thinning process can includegrinding and etching processes or the like. In a specific example, thisprocess can include a wafer backgrinding process followed by stressremoval, which can involve dry etching, CMP polishing, or annealingprocesses.

FIG. 9A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 901 according to an exampleof the present invention. FIG. 9A can represent a method step forforming backside trenches 113 and 114 to allow access to thepiezoelectric layer from the backside of the thinned seed substrate 111.In an example, the first backside trench 113 can be formed within thethinned seed substrate 111 and underlying the topside metal electrode130. The second backside trench 114 can be formed within the thinnedseed substrate 111 and underlying the topside micro-trench 121 andtopside metal plug 146. This substrate is now denoted thinned substrate112. In a specific example, these trenches 113 and 114 can be formedusing deep reactive ion etching (DRIE) processes, Bosch processes, orthe like. The size, shape, and number of the trenches may vary with thedesign of the acoustic resonator device. In various examples, the firstbackside trench may be formed with a trench shape similar to a shape ofthe topside metal electrode or a shape of the backside metal electrode.The first backside trench may also be formed with a trench shape that isdifferent from both a shape of the topside metal electrode and thebackside metal electrode.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 9A. LikeFIGS. 4D and 4E, these figures can represent the method step ofmanufacturing multiple acoustic resonator devices simultaneously. InFIG. 9B, two devices with cap structures are shown on Die #1 and Die #2,respectively. FIG. 9C shows the process of forming backside trenches(113, 114) on each of these dies while also etching a scribe line 115 ordicing line. In an example, the etching of the scribe line 115 providesan optional way to singulate the backside wafer 112.

FIG. 10 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 1000 according to anexample of the present invention. This figure can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147 within the backside trenches of the thinned seed substrate 112. Inan example, the backside metal electrode 131 can be formed underlyingone or more portions of the thinned substrate 112, within the firstbackside trench 113, and underlying the topside metal electrode 130.This process completes the resonator structure within the acousticresonator device. The backside metal plug 147 can be formed underlyingone or more portions of the thinned substrate 112, within the secondbackside trench 114, and underlying the topside micro-trench 121. Thebackside metal plug 147 can be electrically coupled to the topside metalplug 146 and the backside metal electrode 131. In a specific example,the backside metal electrode 130 can include a molybdenum, aluminum,ruthenium, or titanium material, or the like and combinations thereof.The backside metal plug can include a gold material, low resistivityinterconnect metals, electrode metals, or the like. These layers can bedeposited using the deposition methods described previously.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention. These figures show methods ofbonding a backside cap structure underlying the thinned seed substrate112. In FIG. 11A, the backside cap structure is a dry film cap 161,which can include a permanent photo-imagable dry film such as a soldermask, polyimide, or the like. Bonding this cap structure can becost-effective and reliable, but may not produce a hermetic seal. InFIG. 11B, the backside cap structure is a substrate 162, which caninclude a silicon, glass, or other like material. Bonding this substratecan provide a hermetic seal, but may cost more and require additionalprocesses. Depending upon application, either of these backside capstructures can be bonded underlying the first and second backside vias.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. More specifically, these figures describeadditional steps for processing the blind via interposer “602” versionof the top cap structure. FIG. 12A shows an acoustic resonator device1201 with blind vias 152 in the top cap structure. In FIG. 12B, theinterposer substrate 119 is thinned, which forms a thinned interposersubstrate 118, to expose the blind vias 152. This thinning process canbe a combination of a grinding process and etching process as describedfor the thinning of the seed substrate. In FIG. 12C, a redistributionlayer (RDL) process and metallization process can be applied to createtop cap bond pads 160 that are formed overlying the blind vias 152 andare electrically coupled to the blind vias 152. As shown in FIG. 12D, aball grid array (BGA) process can be applied to form solder balls 170overlying and electrically coupled to the top cap bond pads 160. Thisprocess leaves the acoustic resonator device ready for wire bonding 171,as shown in FIG. 12E.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. As shown, device 1300 includes two fullyprocessed acoustic resonator devices that are ready to singulation tocreate separate devices. In an example, the die singulation process canbe done using a wafer dicing saw process, a laser cut singulationprocess, or other processes and combinations thereof.

FIGS. 14A to 14G are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1B. The method for this example of an acoustic resonator can go throughsimilar steps as described in FIGS. 1-5. FIG. 14A shows where thismethod differs from that described previously. Here, the top capstructure substrate 119 and only includes one layer of metallizationwith one or more bottom bond pads 142. Compared to FIG. 6, there are novia structures in the top cap structure because the interconnectionswill be formed on the bottom side of the acoustic resonator device.

FIGS. 14B to 14F depict method steps similar to those described in thefirst process flow. FIG. 14B can represent a method step of bonding thetop cap structure to the piezoelectric layer 120 through the bond pads(140, 142) and the topside metal 141, now denoted as bond pads 144 andtopside metal 145 with topside metal plug 146. FIG. 14C can represent amethod step of thinning the seed substrate 110, which forms a thinnedseed substrate 111, similar to that described in FIG. 8. FIG. 14D canrepresent a method step of forming first and second backside trenches,similar to that described in FIG. 9A. FIG. 14E can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147, similar to that described in FIG. 10. FIG. 14F can represent amethod step of bonding a backside cap structure 162, similar to thatdescribed in FIGS. 11A and 11B.

FIG. 14G shows another step that differs from the previously describedprocess flow. Here, the backside bond pads 171, 172, and 173 are formedwithin the backside cap structure 162. In an example, these backsidebond pads 171-173 can be formed through a masking, etching, and metaldeposition processes similar to those used to form the other metalmaterials. A BGA process can be applied to form solder balls 170 incontact with these backside bond pads 171-173, which prepares theacoustic resonator device 1407 for wire bonding.

FIGS. 15A to 15E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1B. The method for this example can go through similar steps asdescribed in FIG. 1-5. FIG. 15A shows where this method differs fromthat described previously. A temporary carrier 218 with a layer oftemporary adhesive 217 is attached to the substrate. In a specificexample, the temporary carrier 218 can include a glass wafer, a siliconwafer, or other wafer and the like.

FIGS. 15B to 15F depict method steps similar to those described in thefirst process flow. FIG. 15B can represent a method step of thinning theseed substrate 110, which forms a thinned substrate 111, similar to thatdescribed in FIG. 8. In a specific example, the thinning of the seedsubstrate 110 can include a back side grinding process followed by astress removal process. The stress removal process can include a dryetch, a Chemical Mechanical Planarization (CMP), and annealingprocesses.

FIG. 15C can represent a method step of forming a shared backside trench113, similar to the techniques described in FIG. 9A. The main differenceis that the shared backside trench is configured underlying both topsidemetal electrode 130, topside micro-trench 121, and topside metal plug146. In an example, the shared backside trench 113 is a backsideresonator cavity that can vary in size, shape (all possible geometricshapes), and side wall profile (tapered convex, tapered concave, orright angle). In a specific example, the forming of the shared backsidetrench 113 can include a litho-etch process, which can include aback-to-front alignment and dry etch of the backside substrate 111. Thepiezoelectric layer 120 can serve as an etch stop layer for the formingof the shared backside trench 113.

FIG. 15D can represent a method step of forming a backside metalelectrode 131 and a backside metal 147, similar to that described inFIG. 10. In an example, the forming of the backside metal electrode 131can include a deposition and patterning of metal materials within theshared backside trench 113. Here, the backside metal 131 serves as anelectrode and the backside plug/connect metal 147 within the micro-via121. The thickness, shape, and type of metal can vary as a function ofthe resonator/filter design. As an example, the backside electrode 131and via plug metal 147 can be different metals. In a specific example,these backside metals 131, 147 can either be deposited and patterned onthe surface of the piezoelectric layer 120 or rerouted to the backsideof the substrate 112. In an example, the backside metal electrode may bepatterned such that it is configured within the boundaries of the sharedbackside trench such that the backside metal electrode does not come incontact with one or more side-walls of the seed substrate created duringthe forming of the shared backside trench.

FIG. 15E can represent a method step of bonding a backside cap structure162, similar to that described in FIGS. 11A and 11B, following ade-bonding of the temporary carrier 218 and cleaning of the topside ofthe device to remove the temporary adhesive 217. Those of ordinary skillin the art will recognize other variations, modifications, andalternatives of the methods steps described previously.

As used herein, the term “substrate” can mean the bulk substrate or caninclude overlying growth structures such as an aluminum, gallium, orternary compound of aluminum and gallium and nitrogen containingepitaxial region, or functional regions, combinations, and the like.

One or more benefits are achieved over pre-existing techniques using theinvention. In particular, the present device can be manufactured in arelatively simple and cost effective manner while using conventionalmaterials and/or methods according to one of ordinary skill in the art.Using the present method, one can create a reliable single crystal basedacoustic resonator using multiple ways of three-dimensional stackingthrough a wafer level process. Such filters or resonators can beimplemented in an RF filter device, an RF filter system, or the like.Depending upon the embodiment, one or more of these benefits may beachieved. Of course, there can be other variations, modifications, andalternatives.

With 4G LTE and 5G growing more popular by the day, wireless datacommunication demands high performance RF filters with frequenciesaround 5 GHz and higher. Bulk acoustic wave resonators (BAWR), widelyused in such filters operating at frequencies around 3 GHz and lower,are leading candidates for meeting such demands. Current bulk acousticwave resonators use polycrystalline piezoelectric AlN thin films whereeach grain's c-axis is aligned perpendicular to the film's surface toallow high piezoelectric performance whereas the grains' a- or b-axisare randomly distributed. This peculiar grain distribution works wellwhen the piezoelectric film's thickness is around 1 um and above, whichis the perfect thickness for bulk acoustic wave (BAW) filters operatingat frequencies ranging from 1 to 3 GHz. However, the quality of thepolycrystalline piezoelectric films degrades quickly as the thicknessesdecrease below around 0.5 um, which is required for resonators andfilters operating at frequencies around 5 GHz and above.

Single crystalline or epitaxial piezoelectric thin films grown oncompatible crystalline substrates exhibit good crystalline quality andhigh piezoelectric performance even down to very thin thicknesses, e.g.,0.4 um. The present invention provides manufacturing processes andstructures for high quality bulk acoustic wave resonators with singlecrystalline or epitaxial piezoelectric thn films for high frequency BAWfilter applications.

BAWRs require a piezoelectric material, e.g., AlN, in crystalline form,i.e., polycrystalline or single crystalline. The quality of the filmheavy depends on the chemical, crystalline, or topographical quality ofthe layer on which the film is grown. In conventional BAWR processes(including film bulk acoustic resonator (FBAR) or solidly mountedresonator (SMR) geometry), the piezoelectric film is grown on apatterned bottom electrode, which is usually made of molybdenum (Mo),tungsten (W), or ruthenium (Ru). The surface geometry of the patternedbottom electrode significantly influences the crystalline orientationand crystalline quality of the piezoelectric film, requiring complicatedmodification of the structure.

Thus, the present invention uses single crystalline piezoelectric filmsand thin film transfer processes to produce a BAWR with enhancedultimate quality factor and electro-mechanical coupling for RF filters.Such methods and structures facilitate methods of manufacturing andstructures for RF filters using single crystalline or epitaxialpiezoelectric films to meet the growing demands of contemporary datacommunication.

In an example, the present invention provides transfer structures andprocesses for acoustic resonator devices, which provides a flat,high-quality, single-crystal piezoelectric film for superior acousticwave control and high Q in high frequency. As described above,polycrystalline piezoelectric layers limit Q in high frequency. Also,growing epitaxial piezoelectric layers on patterned electrodes affectsthe crystalline orientation of the piezoelectric layer, which limits theability to have tight boundary control of the resulting resonators.Embodiments of the present invention, as further described below, canovercome these limitations and exhibit improved performance andcost-efficiency.

FIGS. 16A-16C through FIGS. 31A-31C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure with asacrificial layer. In these figure series described below, the “A”figures show simplified diagrams illustrating top cross-sectional viewsof single crystal resonator devices according to various embodiments ofthe present invention. The “B” figures show simplified diagramsillustrating lengthwise cross-sectional views of the same devices in the“A” figures. Similarly, the “C” figures show simplified diagramsillustrating widthwise cross-sectional views of the same devices in the“A” figures. In some cases, certain features are omitted to highlightother features and the relationships between such features. Those ofordinary skill in the art will recognize variations, modifications, andalternatives to the examples shown in these figure series.

FIGS. 16A-16C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a piezoelectric film 1620 overlying a growth substrate 1610. Inan example, the growth substrate 1610 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric film 1620 canbe an epitaxial film including aluminum nitride (AlN), gallium nitride(GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim.

FIGS. 17A-17C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first electrode 1710 overlying the surface region of thepiezoelectric film 1620. In an example, the first electrode 1710 caninclude molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials. In a specific example, the first electrode 1710 can besubjected to a dry etch with a slope. As an example, the slope can beabout 60 degrees.

FIGS. 18A-18C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first passivation layer 1810 overlying the first electrode1710 and the piezoelectric film 1620. In an example, the firstpassivation layer 1810 can include silicon nitride (SiN), silicon oxide(SiOx), or other like materials. In a specific example, the firstpassivation layer 1810 can have a thickness ranging from about 50 nm toabout 100 nm.

FIGS. 19A-19C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a sacrificial layer 1910 overlying a portion of the firstelectrode 1810 and a portion of the piezoelectric film 1620. In anexample, the sacrificial layer 1910 can include polycrystalline silicon(poly-Si), amorphous silicon (a-Si), or other like materials. In aspecific example, this sacrificial layer 1910 can be subjected to a dryetch with a slope and be deposited with a thickness of about 1 um.Further, phosphorous doped SiO.sub.2 (PSG) can be used as thesacrificial layer with different combinations of support layer (e.g.,SiNx).

FIGS. 20A-20C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a support layer 2010 overlying the sacrificial layer 1910, thefirst electrode 1710, and the piezoelectric film 1620. In an example,the support layer 2010 can include silicon dioxide (SiO.sub.2), siliconnitride (SiN), or other like materials. In a specific example, thissupport layer 2010 can be deposited with a thickness of about 2-3 um. Asdescribed above, other support layers (e.g., SiNx) can be used in thecase of a PSG sacrificial layer.

FIGS. 21A-21C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofpolishing the support layer 2010 to form a polished support layer 2011.In an example, the polishing process can include a chemical-mechanicalplanarization process or the like.

FIGS. 22A-22C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate flipping thedevice and physically coupling overlying the support layer 2011overlying a bond substrate 2210. In an example, the bond substrate 2210can include a bonding support layer 2220 (SiO.sub.2 or like material)overlying a substrate having silicon (Si), sapphire (Al.sub.2O.sub.3),silicon dioxide (SiO.sub.2), silicon carbide (SiC), or other likematerials. In a specific embodiment, the bonding support layer 2220 ofthe bond substrate 2210 is physically coupled to the polished supportlayer 2011. Further, the physical coupling process can include a roomtemperature bonding process following by a 300 degree Celsius annealingprocess.

FIGS. 23A-23C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the growth substrate 1610 or otherwise the transfer of thepiezoelectric film 1620. In an example, the removal process can includea grinding process, a blanket etching process, a film transfer process,an ion implantation transfer process, a laser crack transfer process, orthe like and combinations thereof.

FIGS. 24A-24C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming an electrode contact via 2410 within the piezoelectric film 1620(becoming piezoelectric film 1621) overlying the first electrode 1710and forming one or more release holes 2420 within the piezoelectric film1620 and the first passivation layer 1810 overlying the sacrificiallayer 1910. The via forming processes can include various types ofetching processes.

FIGS. 25A-25C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second electrode 2510 overlying the piezoelectric film 1621.In an example, the formation of the second electrode 2510 includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching the second electrode 2510 to form anelectrode cavity 2511 and to remove portion 2511 from the secondelectrode to form a top metal 2520. Further, the top metal 2520 isphysically coupled to the first electrode 1720 through electrode contactvia 2410.

FIGS. 26A-26C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first contact metal 2610 overlying a portion of the secondelectrode 2510 and a portion of the piezoelectric film 1621, and forminga second contact metal 2611 overlying a portion of the top metal 2520and a portion of the piezoelectric film 1621. In an example, the firstand second contact metals can include gold (Au), aluminum (Al), copper(Cu), nickel (Ni), aluminum bronze (AlCu), or related alloys of thesematerials or other like materials.

FIGS. 27A-27C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second passivation layer 2710 overlying the second electrode2510, the top metal 2520, and the piezoelectric film 1621. In anexample, the second passivation layer 2710 can include silicon nitride(SiN), silicon oxide (SiOx), or other like materials. In a specificexample, the second passivation layer 2710 can have a thickness rangingfrom about 50 nm to about 100 nm.

FIGS. 28A-28C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the sacrificial layer 1910 to form an air cavity 2810. In anexample, the removal process can include a poly-Si etch or an a-Si etch,or the like.

FIGS. 29A-29C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the second electrode 2510 and the top metal 2520 toform a processed second electrode 2910 and a processed top metal 2920.This step can follow the formation of second electrode 2510 and topmetal 2520. In an example, the processing of these two componentsincludes depositing molybdenum (Mo), ruthenium (Ru), tungsten (W), orother like materials; and then etching (e.g., dry etch or the like) thismaterial to form the processed second electrode 2910 with an electrodecavity 2912 and the processed top metal 2920. The processed top metal2920 remains separated from the processed second electrode 2910 by theremoval of portion 2911. In a specific example, the processed secondelectrode 2910 is characterized by the addition of an energy confinementstructure configured on the processed second electrode 2910 to increaseQ.

FIGS. 30A-30C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 1710 to form a processed firstelectrode 2310. This step can follow the formation of first electrode1710. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 3010 with an electrode cavity,similar to the processed second electrode 2910. Air cavity 2811 showsthe change in cavity shape due to the processed first electrode 3010. Ina specific example, the processed first electrode 3010 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 3010 to increase Q.

FIGS. 31A-31C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 1710, to form a processed firstelectrode 2310, and the second electrode 2510/top metal 2520 to form aprocessed second electrode 2910/processed top metal 2920. These stepscan follow the formation of each respective electrode, as described forFIGS. 29A-29C and 30A-30C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

FIGS. 32A-32C through FIGS. 46A-46C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure withoutsacrificial layer. In these figure series described below, the “A”figures show simplified diagrams illustrating top cross-sectional viewsof single crystal resonator devices according to various embodiments ofthe present invention. The “B” figures show simplified diagramsillustrating lengthwise cross-sectional views of the same devices in the“A” figures. Similarly, the “C” figures show simplified diagramsillustrating widthwise cross-sectional views of the same devices in the“A” figures. In some cases, certain features are omitted to highlightother features and the relationships between such features. Those ofordinary skill in the art will recognize variations, modifications, andalternatives to the examples shown in these figure series.

FIGS. 32A-32C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming apiezoelectric film 3220 overlying a growth substrate 3210. In anexample, the growth substrate 3210 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric film 3220 canbe an epitaxial film including aluminum nitride (AlN), gallium nitride(GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim.

FIGS. 33A-33C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstelectrode 3310 overlying the surface region of the piezoelectric film3220. In an example, the first electrode 3310 can include molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials. In aspecific example, the first electrode 3310 can be subjected to a dryetch with a slope. As an example, the slope can be about 60 degrees.

FIGS. 34A-34C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstpassivation layer 3410 overlying the first electrode 3310 and thepiezoelectric film 3220. In an example, the first passivation layer 3410can include silicon nitride (SiN), silicon oxide (SiOx), or other likematerials. In a specific example, the first passivation layer 3410 canhave a thickness ranging from about 50 nm to about 100 nm.

FIGS. 35A-35C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a supportlayer 3510 overlying the first electrode 3310, and the piezoelectricfilm 3220. In an example, the support layer 3510 can include silicondioxide (SiO.sub.2), silicon nitride (SiN), or other like materials. Ina specific example, this support layer 3510 can be deposited with athickness of about 2-3 um. As described above, other support layers(e.g., SiNx) can be used in the case of a PSG sacrificial layer.

FIGS. 36A-36C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the optional method step of processingthe support layer 3510 (to form support layer 3511) in region 3610. Inan example, the processing can include a partial etch of the supportlayer 3510 to create a flat bond surface. In a specific example, theprocessing can include a cavity region. In other examples, this step canbe replaced with a polishing process such as a chemical-mechanicalplanarization process or the like.

FIGS. 37A-37C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming an air cavity3710 within a portion of the support layer 3511 (to form support layer3512). In an example, the cavity formation can include an etchingprocess that stops at the first passivation layer 3410.

FIGS. 38A-38C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming one or morecavity vent holes 3810 within a portion of the piezoelectric film 3220through the first passivation layer 3410. In an example, the cavity ventholes 3810 connect to the air cavity 3710.

FIGS. 39A-39C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate flipping the device and physicallycoupling overlying the support layer 3512 overlying a bond substrate3910. In an example, the bond substrate 3910 can include a bondingsupport layer 3920 (SiO.sub.2 or like material) overlying a substratehaving silicon (Si), sapphire (Al.sub.2O.sub.3), silicon dioxide(SiO.sub.2), silicon carbide (SiC), or other like materials. In aspecific embodiment, the bonding support layer 3920 of the bondsubstrate 3910 is physically coupled to the polished support layer 3512.Further, the physical coupling process can include a room temperaturebonding process following by a 300 degree Celsius annealing process.

FIGS. 40A-40C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of removing the growthsubstrate 3210 or otherwise the transfer of the piezoelectric film 3220.In an example, the removal process can include a grinding process, ablanket etching process, a film transfer process, an ion implantationtransfer process, a laser crack transfer process, or the like andcombinations thereof.

FIGS. 41A-41C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming an electrodecontact via 4110 within the piezoelectric film 3220 overlying the firstelectrode 3310. The via forming processes can include various types ofetching processes.

FIGS. 42A-42C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a secondelectrode 4210 overlying the piezoelectric film 3220. In an example, theformation of the second electrode 4210 includes depositing molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials; and thenetching the second electrode 4210 to form an electrode cavity 4211 andto remove portion 4211 from the second electrode to form a top metal4220. Further, the top metal 4220 is physically coupled to the firstelectrode 3310 through electrode contact via 4110.

FIGS. 43A-43C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstcontact metal 4310 overlying a portion of the second electrode 4210 anda portion of the piezoelectric film 3220, and forming a second contactmetal 4311 overlying a portion of the top metal 4220 and a portion ofthe piezoelectric film 3220. In an example, the first and second contactmetals can include gold (Au), aluminum (Al), copper (Cu), nickel (Ni),aluminum bronze (AlCu), or other like materials. This figure also showsthe method step of forming a second passivation layer 4320 overlying thesecond electrode 4210, the top metal 4220, and the piezoelectric film3220. In an example, the second passivation layer 4320 can includesilicon nitride (SiN), silicon oxide (SiOx), or other like materials. Ina specific example, the second passivation layer 4320 can have athickness ranging from about 50 nm to about 100 nm.

FIGS. 44A-44C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to another example of the present invention.As shown, these figures illustrate the method step of processing thesecond electrode 4210 and the top metal 4220 to form a processed secondelectrode 4410 and a processed top metal 4420. This step can follow theformation of second electrode 4210 and top metal 4220. In an example,the processing of these two components includes depositing molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials; and thenetching (e.g., dry etch or the like) this material to form the processedsecond electrode 4410 with an electrode cavity 4412 and the processedtop metal 4420. The processed top metal 4420 remains separated from theprocessed second electrode 4410 by the removal of portion 4411. In aspecific example, the processed second electrode 4410 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 4410 to increase Q.

FIGS. 45A-45C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 3310 to form a processed firstelectrode 4510. This step can follow the formation of first electrode3310. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 4510 with an electrode cavity,similar to the processed second electrode 4410. Air cavity 3711 showsthe change in cavity shape due to the processed first electrode 4510. Ina specific example, the processed first electrode 4510 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 4510 to increase Q.

FIGS. 46A-46C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 3310, to form a processed firstelectrode 4510, and the second electrode 4210/top metal 4220 to form aprocessed second electrode 4410/processed top metal 4420. These stepscan follow the formation of each respective electrode, as described forFIGS. 44A-44C and 45A-45C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

FIGS. 47A-47C through FIGS. 59A-59C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure with amultilayer mirror structure. In these figure series described below, the“A” figures show simplified diagrams illustrating top cross-sectionalviews of single crystal resonator devices according to variousembodiments of the present invention. The “B” figures show simplifieddiagrams illustrating lengthwise cross-sectional views of the samedevices in the “A” figures. Similarly, the “C” figures show simplifieddiagrams illustrating widthwise cross-sectional views of the samedevices in the “A” figures. In some cases, certain features are omittedto highlight other features and the relationships between such features.Those of ordinary skill in the art will recognize variations,modifications, and alternatives to the examples shown in these figureseries.

FIGS. 47A-47C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a piezoelectric film 4720 overlying a growth substrate 4710. Inan example, the growth substrate 4710 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric film 4720 canbe an epitaxial film including aluminum nitride (AlN), gallium nitride(GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim.

FIGS. 48A-48C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first electrode 4810 overlying the surface region of thepiezoelectric film 4720. In an example, the first electrode 4810 caninclude molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials. In a specific example, the first electrode 4810 can besubjected to a dry etch with a slope. As an example, the slope can beabout 60 degrees.

FIGS. 49A-49C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a multilayer mirror or reflector structure. In an example, themultilayer mirror includes at least one pair of layers with a lowimpedance layer 4910 and a high impedance layer 4920. In FIGS. 49A-49C,two pairs of low/high impedance layers are shown (low: 4910 and 4911;high: 4920 and 4921). In an example, the mirror/reflector area can belarger than the resonator area and can encompass the resonator area. Ina specific embodiment, each layer thickness is about ¼ of the wavelengthof an acoustic wave at a targeting frequency. The layers can bedeposited in sequence and be etched afterwards, or each layer can bedeposited and etched individually. In another example, the firstelectrode 4810 can be patterned after the mirror structure is patterned.

FIGS. 50A-50C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a support layer 5010 overlying the mirror structure (layers4910, 4911, 4920, and 4921), the first electrode 4810, and thepiezoelectric film 4720. In an example, the support layer 5010 caninclude silicon dioxide (SiO.sub.2), silicon nitride (SiN), or otherlike materials. In a specific example, this support layer 5010 can bedeposited with a thickness of about 2-3 um. As described above, othersupport layers (e.g., SiNx) can be used.

FIGS. 51A-51C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofpolishing the support layer 5010 to form a polished support layer 5011.In an example, the polishing process can include a chemical-mechanicalplanarization process or the like.

FIGS. 52A-52C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate flipping thedevice and physically coupling overlying the support layer 5011overlying a bond substrate 5210. In an example, the bond substrate 5210can include a bonding support layer 5220 (SiO.sub.2 or like material)overlying a substrate having silicon (Si), sapphire (Al.sub.2O.sub.3),silicon dioxide (SiO.sub.2), silicon carbide (SiC), or other likematerials. In a specific embodiment, the bonding support layer 5220 ofthe bond substrate 5210 is physically coupled to the polished supportlayer 5011. Further, the physical coupling process can include a roomtemperature bonding process following by a 300 degree Celsius annealingprocess.

FIGS. 53A-53C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the growth substrate 4710 or otherwise the transfer of thepiezoelectric film 4720. In an example, the removal process can includea grinding process, a blanket etching process, a film transfer process,an ion implantation transfer process, a laser crack transfer process, orthe like and combinations thereof.

FIGS. 54A-54C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming an electrode contact via 5410 within the piezoelectric film 4720overlying the first electrode 4810. The via forming processes caninclude various types of etching processes.

FIGS. 55A-55C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second electrode 5510 overlying the piezoelectric film 4720.In an example, the formation of the second electrode 5510 includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching the second electrode 5510 to form anelectrode cavity 5511 and to remove portion 5511 from the secondelectrode to form a top metal 5520. Further, the top metal 5520 isphysically coupled to the first electrode 5520 through electrode contactvia 5410.

FIGS. 56A-56C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first contact metal 5610 overlying a portion of the secondelectrode 5510 and a portion of the piezoelectric film 4720, and forminga second contact metal 5611 overlying a portion of the top metal 5520and a portion of the piezoelectric film 4720. In an example, the firstand second contact metals can include gold (Au), aluminum (Al), copper(Cu), nickel (Ni), aluminum bronze (AlCu), or other like materials. Thisfigure also shows the method step of forming a second passivation layer5620 overlying the second electrode 5510, the top metal 5520, and thepiezoelectric film 4720. In an example, the second passivation layer5620 can include silicon nitride (SiN), silicon oxide (SiOx), or otherlike materials. In a specific example, the second passivation layer 5620can have a thickness ranging from about 50 nm to about 100 nm.

FIGS. 57A-57C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the second electrode 5510 and the top metal 5520 toform a processed second electrode 5710 and a processed top metal 5720.This step can follow the formation of second electrode 5710 and topmetal 5720. In an example, the processing of these two componentsincludes depositing molybdenum (Mo), ruthenium (Ru), tungsten (W), orother like materials; and then etching (e.g., dry etch or the like) thismaterial to form the processed second electrode 5410 with an electrodecavity 5712 and the processed top metal 5720. The processed top metal5720 remains separated from the processed second electrode 5710 by theremoval of portion 5711. In a specific example, this processing givesthe second electrode and the top metal greater thickness while creatingthe electrode cavity 5712. In a specific example, the processed secondelectrode 5710 is characterized by the addition of an energy confinementstructure configured on the processed second electrode 5710 to increaseQ.

FIGS. 58A-58C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 4810 to form a processed firstelectrode 5810. This step can follow the formation of first electrode4810. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 5810 with an electrode cavity,similar to the processed second electrode 5710. Compared to the twoprevious examples, there is no air cavity. In a specific example, theprocessed first electrode 5810 is characterized by the addition of anenergy confinement structure configured on the processed secondelectrode 5810 to increase Q.

FIGS. 59A-59C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 4810, to form a processed firstelectrode 5810, and the second electrode 5510/top metal 5520 to form aprocessed second electrode 5710/processed top metal 5720. These stepscan follow the formation of each respective electrode, as described forFIGS. 57A-57C and 58A-58C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

In each of the preceding examples relating to transfer processes, energyconfinement structures can be formed on the first electrode, secondelectrode, or both. In an example, these energy confinement structuresare mass loaded areas surrounding the resonator area. The resonator areais the area where the first electrode, the piezoelectric layer, and thesecond electrode overlap. The larger mass load in the energy confinementstructures lowers a cut-off frequency of the resonator. The cut-offfrequency is the lower or upper limit of the frequency at which theacoustic wave can propagate in a direction parallel to the surface ofthe piezoelectric film. Therefore, the cut-off frequency is theresonance frequency in which the wave is travelling along the thicknessdirection and thus is determined by the total stack structure of theresonator along the vertical direction. In piezoelectric films (e.g.,AlN), acoustic waves with lower frequency than the cut-off frequency canpropagate in a parallel direction along the surface of the film, i.e.,the acoustic wave exhibits a high-band-cut-off type dispersioncharacteristic. In this case, the mass loaded area surrounding theresonator provides a barrier preventing the acoustic wave frompropagating outside the resonator. By doing so, this feature increasesthe quality factor of the resonator and improves the performance of theresonator and, consequently, the filter.

In addition, the top single crystalline piezoelectric layer can bereplaced by a polycrystalline piezoelectric film. In such films, thelower part that is close to the interface with the substrate has poorcrystalline quality with smaller grain sizes and a wider distribution ofthe piezoelectric polarization orientation than the upper part of thefilm close to the surface. This is due to the polycrystalline growth ofthe piezoelectric film, i.e., the nucleation and initial film haverandom crystalline orientations. Considering AlN as a piezoelectricmaterial, the growth rate along the c-axis or the polarizationorientation is higher than other crystalline orientations that increasethe proportion of the grains with the c-axis perpendicular to the growthsurface as the film grows thicker. In a typical polycrystalline AlN filmwith about a 1 um thickness, the upper part of the film close to thesurface has better crystalline quality and better alignment in terms ofpiezoelectric polarization. By using the thin film transfer processcontemplated in the present invention, it is possible to use the upperportion of the polycrystalline film in high frequency BAW resonatorswith very thin piezoelectric films. This can be done by removing aportion of the piezoelectric layer during the growth substrate removalprocess. Of course, there can be other variations, modifications, andalternatives.

In an example, the present invention provides a high-performance,ultra-small pass-band Bulk Acoustic Wave (BAW) Radio Frequency (RF)Filter for use in 5.2 GHz Wi-Fi applications covering U-NII-1 plusU-NII-2A bands.

FIG. 60 is a simplified diagram illustrating filter pass-bandrequirements in a radio frequency spectrum according to an example ofthe present invention. As shown, the frequency spectrum 6000 shows arange from 3.0 GHz to 6.0 GHz. Here, a first application band 6010 (3.3GHz-4.2 GHz) is configured for 5G applications. This band includes a 5Gsub-band 6011 (3.3 GHz-3.8 GHz), which includes further LTE sub-bands6012 (3.4 GHz-3.6 GHz), 6013 (3.6 GHz-3.8 GHz), and 6014 (3.55 GHz-3.7GHz). A second application band 6020 (4.4 GHz-5.0 GHz) includes asub-band 6021 for China specific applications. A third application band6030 includes a UNII-1 band 6031 (5.15 GHz-5.25 GHz) and a UNII-2A band6032 (5.25 GHz 5.33 GHz). An LTE band 6033 overlaps the same frequencyrange as the UNII-1 band 6031. Finally, a fourth application band 6040includes a UNII-2C band 6041 (5.490 GHz-5.735 GHz), a UNII-3 band 6042(5.735 GHz-5.85 GHz), and a UNII-4 band 6043 (5.85 GHz-5.925 GHz). AnLTE band 6044 shares the same frequency range as the UNII-2C band 6041,while a sub-band 6045 overlaps the same frequency range as the UNII-4band 6043 and an LTE band 6046 overlaps a smaller subsection of the samefrequency range (5.855 GHz-5.925 GHz). Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

In an embodiment, the present filter utilizes single crystal BAWtechnology as described in the previous figures. This filter provideslow insertion loss and meets the stringent rejection requirementsenabling coexistence with U-NII-2C and U-NII-3 bands. The high-powerrating satisfies the demanding power requirements of the latest Wi-Fistandards.

FIG. 61 is a simplified diagram illustrating an overview of key marketsthat are applications for acoustic wave RF filters according to anexample of the present invention. The application chart 6100 for 5.2 GHzBAW RF filters shows mobile devices, smartphones, automobiles, Wi-Fitri-band routers, tri-band mobile devices, tri-band smartphones,integrated cable modems, Wi-Fi tri-band access points, LTE/LAA smallcells, and the like. A schematic representation of the frequencyspectrum used in a tri-band Wi-Fi system is provided in FIG. 62.

FIG. 62 is a simplified diagram illustrating application areas for 5.2GHz RF filters in Tri-Band Wi-Fi radios according to examples of thepresent invention. As shown, RF filters used by communication devices6210 can be configured for specific applications at three separate bandsof operation. In a specific example, application area 6220 operates at2.4 GHz and includes computing and mobile devices, application area 6230operates at 5.2 GHz and includes television and display devices, andapplication area 6240 operates at 5.6 GHz and includes video gameconsole and handheld devices. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

The present invention includes resonator and RF filter devices usingboth textured polycrystalline piezoelectric materials (deposited usingPVD methods) and single crystal piezoelectric materials (grown using CVDtechnique upon a seed substrate). Various substrates can be used forfabricating the acoustic devices, such silicon substrates of variouscrystallographic orientations and the like. Additionally, the presentmethod can use sapphire substrates, silicon carbide substrates, galliumnitride (GaN) bulk substrates, or aluminum nitride (AlN) bulksubstrates. The present method can also use GaN templates, AlNtemplates, and AlxGa1-xN templates (where x varies between 0.0 and 1.0).These substrates and templates can have polar, non-polar, or semi-polarcrystallographic orientations. Further the piezoelectric materialsdeposed on the substrate can include allows selected from at least oneof the following: AlN, AlN, GaN, InN, InGaN, AlInN, AlInGaN, ScAlN,ScAlGaN, ScGaN, ScN, BAIN, BAlScN, and BN.

The resonator and filter devices may employ process technologiesincluding but not limited to Solidly-Mounted Resonator (SMR), Film BulkAcoustic Resonator (FBAR), or Single Crystal Bulk Acoustic Resonator(XBAW). Representative cross-sections are shown below in FIGS. 63A-63C.For clarification, the terms “top” and “bottom” used in the presentspecification are not generally terms in reference of a direction ofgravity. Rather, the terms “top” and “bottom” are used in reference toeach other in the context of the present device and related circuits.Those of ordinary skill in the art will recognize other variations,modifications, and alternatives.

In an example, the piezoelectric layer ranges between 0.1 and 2.0 um andis optimized to produced optimal combination of resistive and acousticlosses. The thickness of the top and bottom electrodes range between 250.ANG. and 2500 .ANG. and the metal consists of a refractory metal withhigh acoustic velocity and low resistivity. The resonators are“passivated” with a dielectric (not shown in FIGS. 63A-63C) consistingof a nitride and or an oxide and whose range is between 100 .ANG. and2000 .ANG.. The dielectric layer is used to adjust resonator resonancefrequency. Extra care is taken to reduce the metal resistivity betweenadjacent resonators on a metal layer called the interconnect metal. Thethickness of the interconnect metal ranges between 500 .ANG. and 5 um.The resonators contain at least one air cavity interface in the case ofSMRs and two air cavity interfaces in the case of FBARs and XBAWs. Theshape of the resonators selected come from asymmetrical shapes includingellipses, rectangles, and polygons. Further, the resonators containreflecting features near the resonator edge on one or both sides of theresonator.

FIGS. 63A-63C are simplified diagrams illustrating cross-sectional viewsof resonator devices according to various examples of the presentinvention. More particularly, device 6301 of FIG. 63A shows a BAWresonator device including an SMR, FIG. 63B shows a BAW resonator deviceincluding an FBAR, and FIG. 63C shows a BAW resonator device with asingle crystal XBAW. As shown in SMR device 6301, a reflector device6320 is configured overlying a substrate member 6310. The reflectordevice 6320 can be a Bragg reflector or the like. A bottom electrode6330 is configured overlying the reflector device 6320. Apolycrystalline piezoelectric layer 6340 is configured overlying thebottom electrode 6330. Further, a top electrode 6350 is configuredoverlying the polycrystalline layer 6340. As shown in the FBAR device6302, the layered structure including the bottom electrode 6330, thepolycrystalline layer 6340, and the top electrode 6350 remains the same.The substrate member 6311 includes an air cavity 6312, and a dielectriclayer is formed overlying the substrate member 6311 and covering the aircavity 6312. As shown in XBAW device 6303, the substrate member 6311also contains an air cavity 6312, but the bottom electrode 6330 isformed within a region of the air cavity 6312. A single crystalpiezoelectric layer is formed overlying the substrate member 6311, theair cavity 6312, and the bottom electrode 6341. Further, a top electrode6350 is formed overlying a portion of the single crystal layer 6341.These resonators can be scaled and configured into circuitconfigurations shown in FIGS. 64A-64C.

The RF filter circuit can comprise various circuit topologies, includingmodified lattice (“I”) 6401, lattice (“II”) 6402, and ladder (“III”)6403 circuit configurations, as shown in FIGS. 64A, 64B, and 64C,respectively. These figures are representative lattice and ladderdiagrams for acoustic filter designs including resonators and otherpassive components. The lattice and modified lattice configurationsinclude differential input ports 6410 and differential output ports6450, while the ladder configuration includes a single-ended input port6411 and a single-ended output port 6450. In the lattice configurations,nodes are denoted by top nodes (t1-t3) and bottom nodes (b1-b3), whilein the ladder configuration the nodes are denoted as one set of nodes(n1-n4). The series resonator elements (in cases I, II, and III) areshown with white center elements 6421-6424 and the shunt resonatorelements have darkened center circuit elements 6431-6434. The serieselements resonance frequency is higher than the shunt elements resonancefrequency in order to form the filter skirt at the pass-band frequency.The inductors 6441-6443 shown in the modified lattice circuit diagram(FIG. 64A) and any other matching elements can be included eitheron-chip (in proximity to the resonator elements) or off-chip (nearby tothe resonator chip) and can be used to adjust frequency pass-band and/ormatching of impedance (to achieve the return loss specification) for thefilter circuit. The filter circuit contains resonators with at least tworesonance frequencies. The center of the pass-band frequency can beadjusted by a trimming step (using an ion milling technique or otherlike technique) and the shape the filter skirt can be adjusted bytrimming individual resonator elements (to vary the resonance frequencyof one or more elements) in the circuit.

In an example, the present invention provides an RF filter circuitdevice in a ladder configuration. The device can include an input port,a first node coupled to the input port, a first resonator coupledbetween the first node and the input port. A second node is coupled tothe first node and a second resonator is coupled between the first nodeand the second node. A third node is coupled to the second node and athird resonator is coupled between the second node and the third node. Afourth node is coupled to the third node and a fourth resonator iscoupled between the third node and the output port. Further, an outputport is coupled to the fourth node. Those of ordinary skill in the artwill recognize other variations, modifications, and alternatives.

Each of the first, second, third, and fourth resonators can include acapacitor device. Each such capacitor device can include a substratemember, which has a cavity region and an upper surface region contiguouswith an opening in the first cavity region. Each capacitor device caninclude a bottom electrode within a portion of the cavity region and apiezoelectric material overlying the upper surface region and the bottomelectrode. Also, each capacitor device can include a top electrodeoverlying the single crystal material and the bottom electrode, as wellas an insulating material overlying the top electrode and configuredwith a thickness to tune the resonator.

The device also includes a serial configuration includes the input port,the first node, the first resonator, the second node, the secondresonator, the third node, the third resonator, the fourth resonator,the fourth node, and the output port. A separate shunt configurationresonator is coupled to each of the first, second, third, fourth nodes.A parallel configuration includes the first, second, third, and fourthshunt configuration resonators. Further, a circuit response can beconfigured between the input port and the output port and configuredfrom the serial configuration and the parallel configuration to achievea transmission loss from a pass-band having a characteristic frequencycentered around 5.2 GHz and having a bandwidth from 5.170 GHz to 5.330GHz such that the characteristic frequency centered around 5.2 GHz istuned from a lower frequency ranging from about 4 GHz to 5.1 GHz.

In a specific example, the first, second, third, and fourthpiezoelectric materials are each essentially a single crystal aluminumnitride bearing material or aluminum scandium nitride bearing material,a single crystal gallium nitride bearing material or gallium aluminumbearing material, or the like. In another specific embodiment, thesepiezoelectric materials each comprise a polycrystalline aluminum nitridebearing material or aluminum scandium bearing material, or apolycrystalline gallium nitride bearing material or gallium aluminumbearing material, or the like.

In a specific example, the serial configuration forms a resonanceprofile and an anti-resonance profile. The parallel configuration alsoforms a resonance profile and an anti-resonance profile. These profilesare such that the resonance profile from the serial configuration isoff-set with the anti-resonance profile of the parallel configuration toform the pass-band.

In a specific example, the pass-band is characterized by a band edge oneach side of the pass-band and having an amplitude difference rangingfrom 10 dB to 60 dB. The pass-band has a pair of band edges; each ofwhich has a transition region from the pass-band to a stop band suchthat the transition region is no greater than 250 MHz. In anotherexample, pass-band can include a pair of band edges and each of theseband edges can have a transition region from the pass-band to a stopband such that the transition region ranges from 5 MHz to 250 MHz.

In a specific example, each of the first, second, third, and fourthinsulating materials comprises a silicon nitride bearing material or anoxide bearing material configured with a silicon nitride material anoxide bearing material.

In a specific example, the present device can further include severalfeatures. The device can further include a rejection band at a frequencygreater than the pass-band. This rejection band can range from 5.490 GHzto 5.835 GHz. The device can further include an insertion loss of 2.1 dBand an amplitude variation characterizing the pass-band of 0.7 dB. Also,the device can include an attenuation of up to 40 dB for a frequencyrange of 1 GHz to 5 GHz or an attenuation of up to 48 dB for a frequencyrange of 5.9 GHz to 11 GHz. The device can further include a return losscharacterizing the pass-band of up to 15 dB and the device can beoperable from −40 Degrees Celsius to 85 Degrees Celsius. The device canfurther include a maximum power within the pass-band of 30 dBm or 1Watt. Further, the pass-band can be configured for a U-NII-1+U-NII-2.ANG. bands and for an IEEE 802.11a channel plan.

In a specific example, the present device can be configured as a bulkacoustic wave (BAW) filter device. Each of the first, second, third, andfourth resonators can be a BAW resonator. Similarly, each of the first,second, third, and fourth shunt resonators can be BAW resonators. Thepresent device can further include one or more additional resonatordevices numbered from N to M, where N is four and M is twenty.Similarly, the present device can further include one or more additionalshunt resonator devices numbered from N to M, where N is four and M istwenty.

In an example, the present invention provides an RF circuit device in alattice configuration. The device can include a differential input port,a top serial configuration, a bottom serial configuration, a firstlattice configuration, a second lattice configuration, and adifferential output port. The top serial configuration can include afirst top node, a second top node, and a third top node. A first topresonator can be coupled between the first top node and the second topnode, while a second top resonator can be coupled between the second topnode and the third top node. Similarly, the bottom serial configurationcan include a first bottom node, a second bottom node, and a thirdbottom node. A first bottom resonator can be coupled between the firstbottom node and the second bottom node, while a second bottom resonatorcan be coupled between the second bottom node and the third bottom node.

In an example, the first lattice configuration includes a first shuntresonator cross-coupled with a second shunt resonator and coupledbetween the first top resonator of the top serial configuration and thefirst bottom resonator of the bottom serial configuration. Similarly,the second lattice configuration can include a first shunt resonatorcross-coupled with a second shunt resonator and coupled between thesecond top resonator of the top serial configuration and the secondbottom resonator of the bottom serial configuration. The top serialconfiguration and the bottom serial configuration can each be coupled toboth the differential input port and the differential output port.

In a specific example, the device further includes a first balun coupledto the differential input port and a second balun coupled to thedifferential output port. The device can further include an inductordevice coupled between the differential input and output ports. In aspecific example, the device can further include a first inductor devicecoupled between the first top node of the top serial configuration andthe first bottom node of the bottom serial configuration; a secondinductor device coupled between the second top node of the top serialconfiguration and the second bottom node of the bottom serialconfiguration; and a third inductor device coupled between the third topnode of the top serial configuration and the third bottom node of thebottom serial configuration.

The packaging approach includes but is not limited to wafer levelpackaging (WLP), WLP-plus-cap wafer approach, flip-chip, chip and bondwire, as shown in FIGS. 65 and 66. One or more RF filter chips and oneor more filter bands can be packaged within the same housingconfiguration. Each RF filter band within the package can include one ormore resonator filter chips and passive elements (capacitors, inductors)can be used to tailor the bandwidth and frequency spectrumcharacteristic. For a tri-band Wi-Fi system application, a packageconfiguration including three RF filter bands, including the 2.4 GHz,5.2 GHz, and 5.6 GHz band-pass solutions is capable using the BAW RFfilter technology. The 2.4 GHz filter solution can be either surfaceacoustic wave (SAW) or BAW, whereas the 5.2 GHz and 5.6 GHz bands arelikely BAW given the high-frequency capability of BAW.

FIG. 65A is a simplified diagram illustrating a packing approachaccording to an example of the present invention. As shown, device 6501is packaged using a conventional die bond of an RF filter die 6510 tothe base 6520 of a package and metal bond wires 6530 to the RF filterchip from the circuit interface 6540.

FIG. 65B is as simplified diagram illustrating a packing approachaccording to an example of the present invention. As shown, device 6602is packaged using a flip-mount wafer level package (WLP) showing the RFfilter silicon die 6510 mounted to the circuit interface 6540 usingcopper pillars 6531 or other high-conductivity interconnects.

FIG. 66 is a simplified diagram illustrating a packing approachaccording to an example of the present invention. Device 6600 shows analternate version of a WLP utilizing a BAW RF filter circuit MEMS device6630 and a substrate 6610 to a cap wafer 6640. In an example, the capwafer 6640 may include thru-silicon-vias (TSVs) to electrically connectthe RF filter MEMS device 6630 to the topside of the cap wafer (notshown in the figure). The cap wafer 6640 can be coupled to a dielectriclayer 6620 overlying the substrate 6610 and sealed by sealing material6650.

In an example, the present filter passes frequencies in the range of5.17 to 5.33 GHz and rejects frequencies outside of this pass-band.Additional features of the 5.2 GHz acoustic wave filter circuit areprovided below. The circuit symbol which is used to reference the RFfilter building block is provided in FIG. 67. The electrical performancespecifications of the 5.2 GHz filter are provided in FIG. 68 and thepass-band performance of the filter is provided in FIG. 69.

In various examples, the present filter can have certain features. Thedie configuration can be less than 2 mm.times.2 mm.times.0.5 mm; in aspecific example, the die configuration is typically less than 1mm.times.1 mm.times.0.2 mm. The packaged device has an ultra-small formfactor, such as a 2 mm.times.2.5 mm.times.0.9 mm using a conventionalchip and bond wire approach, shown in FIG. 65. WLP package approachescan provide smaller form factors. In a specific example, the device isconfigured with a single-ended 50-Ohm antenna, and transmitter/receiver(Tx/Rx) ports. The high rejection of the device enables coexistence withadjacent Wi-Fi UNIT bands. The device is also be characterized by a highpower rating (maximum+30 dBm), a low insertion loss pass-band filterwith less than 2.5 dB transmission loss, and performance over atemperature range from −40 degrees Celsius to +85 degrees Celsius.Further, in a specific example, the device is RoHS (Restriction ofHazardous Substances) compliant and uses Pb-free (lead-free) packaging.

FIG. 67 is a simplified circuit diagram illustrating a 2-port BAW RFfilter circuit according to an example of the present invention. Asshown, circuit 6700 includes a first port (“Port 1”) 6711, a second port(“Port 2”) 6712, and a filter 6720. The first port represents aconnection from a transmitter (TX) or received (RX) to the filter 6720and the second port represents a filter connection from the filter 6720to an antenna (ANT).

FIG. 68 is a simplified table of filter parameters according to anexample of the present invention. As shown, table 6800 includeselectrical specifications for a 5.2 GHz RF resonator filter circuit. Thecircuit parameters are provided along with the specification units,minimum, along with typical and maximum specification values.

FIG. 69 is a simplified graph representing insertion loss over frequencyaccording to an example of the present invention. As shown, graph 6900represents a narrowband measured vs. modeled response for 5.2 GHz RFfilter using a ladder RF filter circuit configuration. The modeled curve6910 is the transmission loss (s21) predicted from a linear simulationtool incorporation non-linear, full 3-dimensional (3D) electromagnetic(EM) simulation. The measured curve 6920 is the s21 measured fromscattering parameters (s-parameters) taken from a network analyzer testsystem.

In an example, the present invention provides a front end module (FEM)for a 5.2 GHz Wi-Fi acoustic wave resonator RF filter circuit. Thedevice can include a power amplifier (PA), a 5.2 GHz resonator, and adiversity switch. In a specific example, the device can further includea low noise amplifier (LNA). The PA is electrically coupled to an inputnode and can be configured to a DC power detector or an RF powerdetector. The resonator can be configured between the PA and thediversity switch, or between the diversity switch and an antenna. TheLNA may be configured to the diversity switch or be electricallyisolated from the switch. Another 5.2 GHZ resonator may be configuredbetween the diversity switch and the LNA. In a specific example, thisdevice integrates a 5.2 GHz PA, a 5.2 GHZ bulk acoustic wave (BAW) RFfilter, a single pole two throw (SP2T) switch, and an optionalbypassable low noise amplifier (LNA) into a single device. FIGS. 70-74show five examples of FEMS according to various embodiments of thepresent invention. In each example, the LNA may be omitted to produce atransmit module only. In the following figures, the reference numberscheme for the elements of these FEMs remains the same across FIGS.70-74 except for the first two digits that correspond to the figurenumber.

FIG. 70 is a simplified circuit block diagram illustrating a front endmodule according to an example of the present invention. As shown,device 7000 includes a PA 7010, a 5.2 GHz resonator 7020, a diversityswitch 7030, and an LNA 7040. Here, the input of the PA 7010 iselectrically coupled to an input node (shown as TX_IN [2]). In aspecific example, the PA can be a 5.2 GHz PA. An inductor 7011 canelectrically coupled to the input node as well. The 5.2 GHz resonator7020 is electrically coupled to the output of the PA 7010. In specificexample, the resonator 7020 can be a 5.2 BAW resonator.

The diversity switch 7030 shown here is a single pole two throw (SP2T)switch. One of the throws is electrically coupled to the 5.2 GHzresonator 7020 while the other throw is electrically coupled to anoutput node (shown as RX OUT [14]). In a specific example, a couplingcapacitor 7031 can be configured between the switch 7030 and the outputnode. The pole, which can switch between the two throws, is electricallycoupled to an antenna (shown as ANT [12]). In a specific example, acoupling capacitor 7032 can be configured between the switch 7030 andthe antenna.

In this case, the LNA 7040 is configured separately from the previouscircuit elements and is electrically coupled to an LNA input (shown asLNA_IN [16]) and an LNA output (shown as LNA OUT [17]). As previouslydiscussed, the LNA 7040 may be omitted, which would result in a devicethat is a transmit module only. In a specific embodiment, couplingcapacitors 7041 and 7042 can be configured between the LNA 7040 and theLNA input and LNA output, respectively. A signal filter 7043 can beconfigured between the LNA and coupling capacity 7041. In this case, thesignal filter 7043 is a bandstop filter. Further, the LNA 7040 can beconfigured in a switched feedback loop 7044. In a specific example, theLNA 7040 can be a bypassable LNA.

In an example, the device 7000 can be configured with a power detector,which can be a DC power detector or an RF power detector. A DC powerdetector has a voltage output and would be electrically coupled to thePA at a DC power detect node (shown as DC_PDET [6]). In a specificexample, a diode is configured between the PA and the DC power detector.An RF power detector has an RF output from a directional coupler 7013,which is configured at the output of the PA.

In an example, the present device design provides a compact form factorand integrated matching minimizes layout area in applications. The PAcan be optimized for a 5V supply voltage that conserves powerconsumption while maintaining a high linear output power and throughput.Also, an integrated BAW filter reduces the overall size for Wi-Fi radioapplications and allows coexistence between the 5.2 GHz radio band andadjacent 2.4 GHz and 5.6 GHz bands in a tri-band router configuration.Those of ordinary skill in the art will recognize other variations,modifications, and alternatives to the above.

FIG. 71 is a simplified circuit block diagram illustrating a front endmodule according to an example of the present invention. The referencenumber scheme is the same as in FIG. 70 except that the first two digitsreferencing “71.” As shown, device 7100 is similar to device 7000 ofFIG. 70 except for the configuration of the 5.2 GHz resonator 7120.Here, the resonator 7120 is configured between the pole of the diversityswitch 7130 and the antenna, as well as the coupling capacitor 7132. Ofcourse, there can be other variations, modifications, and alternatives.

FIG. 72 is a simplified circuit block diagram illustrating a front endmodule according to an example of the present invention. The referencenumber scheme is the same as in FIG. 70 except that the first two digitsreference “72.” As shown, device 7200 is similar to device 7000 exceptthat there is an additional 5.2 GHz resonator 7221 configured betweenone of the throws of the diversity switch 7230 and the input to the LNA7240, as well as the signal filter 7243. In this example, the switch7230 is not coupled to the output node, and the LNA is not coupled tothe LNA input node. Similar to the first resonator 7220, the secondresonator 7221 can also be a 5.2 GHz BAW resonator. Of course, there canbe other variations, modifications, and alternatives.

FIG. 73 is a simplified circuit block diagram illustrating a front endmodule according to an example of the present invention. The referencenumber scheme is the same as in FIG. 70 except that the first two digitsreference “73.” As shown, device 7300 is similar to device 7200 of FIG.72 except that the diversity switch 7330 is a single pole three throw(SP3T) switch and the LNA 7340 no longer includes the switched feedbackloop. Rather, the output of the LNA 7340 is electrically coupled to thethird throw of the switch 7340. Of course, there can be othervariations, modifications, and alternatives.

FIG. 74 is a simplified circuit block diagram illustrating a front endmodule according to an example of the present invention. The referencenumber scheme is the same as in FIG. 70 except that the first two digitsreference “74.” As shown, device 7400 is similar to device 7100 of FIG.71 by having the 5.2 GHz resonator 7420 configured between the switch7030 and the antenna, but also similar to device 7300 of FIG. 73 byhaving the output of the LNA 7440 electrically coupled to a third throwof switch 7430, which is a SP3T switch. Of course, there can be othervariations, modifications, and alternatives.

As appreciated by the present inventors, in some embodiments accordingto the invention, piezoelectric based BAW resonator filters describedabove (for example, in reference to FIG. 64A-C) may be further improvedby replacing the resonator 6421 with (or the addition of) arejection-band series resonator that is configured to have ananti-resonant frequency in a rejection-band of frequencies that is belowthe pass-band. In some approaches a rejection-band shunt resonator canbe added across the input to the resonator 6421, where therejection-band shunt resonator is configured to have a resonantfrequency in a rejection-band that is above the pass-band. It will beunderstood that the anti-resonant frequencies of the rejection-bandseries resonators coupled to the inputs and the outputs of the filtercan be different and may overlap one another. Still further, theresonant frequencies of the rejection-band shunt resonators coupled tothe inputs and the outputs of the filter can be different and mayoverlap one another.

Accordingly, BAW resonator filters according to embodiments of theinvention can be utilized to improve the rejection band performance offilters configured to provide a pass-band of 5.17 GHz to 5.33 GHz. BAWresonator filters according to embodiments of the invention can also beutilized to improve the rejection band performance of filters configuredto provide a pass-band of 5.49 GHz to 5.835 GHz. It will be understoodthat embodiments according to the invention may be provided by theinclusion of at least one rejection-band series or shunt resonatorcoupled to either the input or the output of a BAW resonator filter.Further, a BAW resonator filter can be any topology filter circuit, suchas a ladder or lattice topology.

In still other embodiments, a BAW resonator filter that includes therejection-band series resonators can be combined with a BAW resonatorfilter that includes the rejection-band shunt resonators along with aswitch to select one of the BAW resonator filters for operation. Forexample, in a first state the switch may couple an input signal to theBAW resonator filter that includes the rejection-band series resonators,whereas in a second state the switch may couple the input signal to theBAW resonator filter that includes the rejection-band shunt resonators.Accordingly, in some embodiments two different BAW resonator filters(each having a different pass-band of frequencies) can be integratedinto a single device where the switch can be used to select theparticular BAW resonator filter for a particular application.

It will be further understood that the rejection-band series resonatorscan be formed using a rejection-band mass load structure that is greaterin mass than a pass-band mass load structure on the pass-band seriesresonators. Accordingly, methods used to form the pass-band resonatorscan be adapted to form the rejection-band series resonators describedherein by increasing the mass loading on the rejection band resonatorrelative to that used to form the pass-band resonators. For example, thefirst rejection-band series resonators can be formed with arejection-band mass load structure that is greater in mass than apass-band mass load structure on the pass-band shunt resonators. Stillfurther, the rejection-band series resonator can include arejection-band mass load structure that is greater in mass than thepass-band mass load structure.

FIG. 75 is a schematic illustration of a BAW resonator filter 7500including a BAW resonator pass-band filter ladder 7505 and first andsecond rejection-band series resonators 7510 and 7515 in someembodiments according to the invention. According to the FIG. 75, aninput node of the BAW resonator pass-band filter ladder 7505 is coupledto the first rejection-band series resonator 7510 and an output node ofthe BAW resonator pass-band filter ladder 7505 is coupled to the secondrejection-band series resonator 7515.

FIG. 76 is a graph illustrating anti-resonant frequencies of first andsecond rejection-band series resonators 7510 and 7515 in the BAWresonator filter of FIG. 75 in some embodiments according to theinvention. According to FIG. 76, the BAW resonator filter of FIG. 75provides a pass-band filter with a pass-band frequency range of about5.49 GHz to about 5.835 GHz. The first and second rejection-band seriesresonators 7510 and 7515 are configured to provide anti-resonantfrequency peaks 7520 and 7525 and rejection nulls 7607 and 7608 belowand adjacent to the lower edge of the pass-band. It will be understoodthat although the rejection nulls 7607 and 7608 in FIG. 76 are below andadjacent to the lower edge of the pass-band, in some embodiments thecorresponding rejection nulls may be below but not necessarily adjacentto the lower edge of the pass-band. In some embodiments, theanti-resonant frequencies peaks 7520 and 7525 are approximately alignedwith the rejection nulls 7607 and 7608 in the BAW resonator filterresponse 7524 in the rejection-band of frequencies that are below andadjacent to a lower edge of the pass-band of frequencies.

As described herein, in some embodiments according to the invention theresonant or anti-resonant frequency peaks associated with series orshunt rejection band resonators can be aligned with rejection nullsexhibited in the response of the filter circuit. It will be understood,however, that in some embodiments the resonant or anti-resonantfrequency peaks associated with series or shunt rejection bandresonators can provide the rejection nulls as part of the filterresponse without alignment to otherwise existing rejection nullsincluded in the filter response.

As appreciated by the present inventors, the alignment of theanti-resonant frequencies peaks 7520 and 7525 from first and secondrejection-band series resonators 7510 and 7515 with the rejection nullsin the filter response can provide a combined attenuation in therejection-band of frequencies that is greater than the attenuation thatwould be provided without the inclusion of the first and secondrejection-band series resonators 7510 and 7515, as illustrated by thefilter response 7524 in FIG. 76. In some embodiments, the inclusion ofthe rejection-band series resonators 7510 and 7515, with the alignmentdescribed herein, can provide at least about an additional 5 dB of theattenuation that would be provided without the inclusion of the firstand second rejection-band series resonators 7510 and 7515. In someembodiments, the inclusion of the rejection-band series resonators 7510and 7515, with the alignment described herein, can provide at leastabout an additional 10 dB of attenuation to the filter response.

In some embodiments the resonant frequency peaks 7526 of the pass-bandseries resonators and the anti-resonant frequency peaks 7530 of thepass-band shunt resonators are located at about a center of thepass-band of frequencies. Still further, the resonant frequency peaks7535 of the pass-band shunt resonators are located below or at about thelower edge of the pass-band and the anti-resonant frequency peaks 7609and 7610 of the pass-band series resonators are located at about orabove an upper edge of the pass-band.

FIG. 80 is a schematic illustration of a BAW resonator filter includingthe BAW resonator pass-band filter lattice of FIG. 64A including firstand second rejection-band series resonators 8010 and 8015 in someembodiments according to the invention. FIG. 81 is a schematicillustration of a BAW resonator filter including the BAW resonatorpass-band filter lattice of FIG. 64B including first and secondrejection-band series resonators 8110 and 8115 in some embodimentsaccording to the invention. According to FIGS. 80 and 81, the first andsecond rejection-band series resonators can also be added to the inputand output nodes, respectively, of a BAW resonator pass-band filterlattice, such as that shown in FIGS. 64A and 64B, to further improve therejection performance.

FIG. 82 is a graph representative of the BAW resonator filter response8420 of FIGS. 80 and 81 including the anti-resonant frequencies of thefirst and second rejection-band series resonators 8010/8015 and8110/8115 in some embodiments according to the invention. According toFIG. 82 the anti-resonance frequency peaks 8225 and 8220 associated withthe first and second rejection-band series resonators 8010/8015 and8110/8115 can be approximately aligned with the rejection nulls 7607 and7608 in the BAW resonator filter response 8240 in the rejection-band offrequencies that are below and adjacent to a lower edge of the pass-bandof frequencies. It will be understood that although the rejection nulls7607 and 7608 in FIG. 82 are below and adjacent to the lower edge of thepass-band, in some embodiments the corresponding rejection nulls may bebelow but not necessarily adjacent to the lower edge of the pass-band.As appreciated by the present inventors, the alignment of theanti-resonant frequency peaks from first and second rejection-bandseries resonators 8010/8015 and 8110/8115 with the rejection nulls 7607and 7608 can provide a combined attenuation in the rejection-band offrequencies that is greater than the attenuation that would be providedwithout the inclusion of the first and second rejection-band seriesresonators 8010/8015 and 8110/8115. In some embodiments, the inclusionof the rejection-band series resonators 8010/8015 and 8110/8115, withthe alignment described herein, can provide at least about an additional5 dB of the attenuation that would be provided without the inclusion ofthe first and second rejection-band series resonators 8010/8015 and8110/8115. In some embodiments, the inclusion of the rejection-bandseries resonators 8010/8015 and 8110/8115, with the alignment describedherein, can provide at least about an additional 10 dB of attenuation.

FIG. 77 is a schematic illustration of a BAW resonator filter 7700including a BAW resonator pass-band filter ladder 7705 and first andsecond rejection-band shunt resonators 7710 and 7715 in some embodimentsaccording to the invention. According to the FIG. 77, an input node ofthe BAW resonator pass-band filter ladder 7505 is coupled to the firstrejection-band shunt resonator 7710 and an output node of the BAWresonator pass-band filter ladder 7505 is coupled to the secondrejection-band shunt resonator 7515.

FIG. 78 is a graph illustrating resonant frequencies of first and secondrejection-band shunt resonators 7710 and 7715 in the BAW resonatorfilter 7700 of FIG. 77 in some embodiments according to the invention.According to FIG. 78, the BAW resonator filter of FIG. 77 provides apass-band filter with a pass-band frequency range of about 5.17 GHz toabout 5.33 GHz. The first and second rejection-band shunt resonators7710 and 7715 are configured to provide resonant frequency peaks 7805and 7806 and can be aligned with rejection nulls 7807 and 7808 in thefilter response 7824 above the pass-band. It will be understood thatalthough the rejection nulls 7807 and 7808 in FIG. 78 are above thepass-band, in some embodiments the corresponding rejection nulls may beadjacent to and above the upper edge of the pass-band. In someembodiments the resonant frequency peaks 7815 of the pass-band seriesresonators and the anti-resonant frequency peaks 7810 of the pass-bandshunt resonators are located at about a center of the pass-band offrequencies. Still further, the resonant frequency peaks 7820 of thepass-band shunt resonators are located below a lower edge of thepass-band and the anti-resonant frequency peaks 7811 and 7812 of thepass-band series resonators can be located above and adjacent to anupper edge of the pass-band.

As appreciated by the present inventors, the alignment of the resonantfrequencies peaks 7805 and 7806 from first and second rejection-bandshunt resonators 7710 and 7715 with the rejection nulls 7807 and 7808 inthe filter response can provide a combined attenuation in therejection-band of frequencies that is greater than the attenuation thatwould be provided without the inclusion of the first and secondrejection-band shunt resonators 7710 and 7715. In some embodiments, theinclusion of the rejection-band shunt resonators 7710 and 7715, with thealignment described herein, can provide at least about an additional 5dB of the attenuation that would be provided without the inclusion ofthe first and second rejection-band shunt resonators 7710 and 7715. Insome embodiments, the inclusion of the rejection-band shunt resonators7710 and 7715, with the alignment described herein, can provide at leastabout an additional 10 dB of attenuation.

FIG. 83 is a schematic illustration of a BAW resonator filter includingthe BAW resonator pass-band filter lattice 6401 of FIG. 64A includingfirst and second rejection-band shunt resonators 8310 and 8315 in someembodiments according to the invention. FIG. 84 is a schematicillustration of a BAW resonator filter including the BAW resonatorpass-band filter lattice 6402 of FIG. 64B including first and secondrejection-band shunt resonators 8410 and 8415 in some embodimentsaccording to the invention. According to FIGS. 83 and 84, the first andsecond rejection-band shunt resonators can also be added to the inputand output nodes, respectively, of a BAW resonator pass-band filterlattice, such as that shown in FIGS. 64A and 64B, to further improve therejection performance.

FIG. 85 is a graph representative of the BAW resonator filter response8524 of FIGS. 83 and 84 including the resonant frequencies of the firstand second rejection-band shunt resonators 8310/8315 and 8410/8415 insome embodiments according to the invention. According to FIG. 85 theresonant frequency peaks 7805 and 7806 associated with the first andsecond rejection-band shunt resonators 8310/8315 and 8410/8415 can beapproximately aligned with the rejection nulls 7807 and 7808 in the BAWresonator filter response 8524 in the rejection-band of frequencies thatare above an upper edge of the pass-band of frequencies. It will beunderstood that although the rejection nulls 7807 and 7808 in FIG. 85are above the pass-band, in some embodiments the corresponding rejectionnulls may be adjacent to and above the upper edge of the pass-band. Asappreciated by the present inventors, the alignment of the resonantfrequency peaks from first and second rejection-band shunt resonators8310/8315 and 8410/8415 with the rejection nulls 8707 band 8708 canprovide a combined attenuation in the rejection-band of frequencies thatis greater than the attenuation that would be provided without theinclusion of the first and second rejection-band shunt resonators8310/8315 and 8410/8415. In some embodiments, the inclusion of therejection-band shunt resonators 8310/8315 and 8410/8415, with thealignment described herein, can provide at least about an additional 5dB of the attenuation that would be provided without the inclusion ofthe first and second rejection-band shunt resonators 8310/8315 and8410/8415. In some embodiments, the inclusion of the rejection-bandshunt resonators 8310/8315 and 8410/8415, with the alignment describedherein, can provide at least about an additional 10 dB of attenuation.

FIG. 79 is a schematic illustration of a combined BAW resonator filter7900 including a BAW resonator pass-band filter ladder 7505 coupled tofirst and second rejection-band series resonators and a BAW resonatorpass-band filter ladder 7705 coupled to first and second rejection-bandshunt resonators. The input and output of BAW resonator pass-band filterladder 7505 and the BAW resonator pass-band filter ladder 7705 arecontrolled by setting the switches 7905/7910 in some embodimentsaccording to the invention. According to FIG. 79, in a first state theswitches 7905/7910 may couple the input signal to the BAW resonatorpass-band filter ladder 7505 via the input rejection-band seriesresonator and couple the output of the BAW resonator pass-band filterladder 7505 to the output signal of the BAW resonator filter 7900 viathe output rejection-band series resonator, whereas in a second statethe switches 7905/7910 may couple the input signal to the BAW resonatorpass-band filter ladder 7705 via the input rejection-band shuntresonator and couple the output of the BAW resonator pass-band filterladder 7705 to the output signal of the BAW resonator filter 7900 viathe output rejection-band shunt resonator. Although the combined BAWresonator filter 7900 of FIG. 79 shows first and second ladder typefilter circuit topology, it will be understood that any topology filtercircuit, such as a lattice or modified lattice, may also be used in someembodiments according to the invention. Still further, in someembodiments, a combination of ladder filter circuits and lattice filtercircuits may be included in the BAW resonator filter 7900. Stillfurther, more than two filter circuits may be included in the BAWresonator filter 7900 along with more switches that are configured andoperated to select the filter to be used.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. Therefore, the above description and illustrations shouldnot be taken as limiting the scope of the present invention which isdefined by the appended claims.

What is claimed:
 1. A Bulk Acoustic Wave (BAW) resonator filtercomprising: a BAW resonator pass-band filter circuit, the BAW resonatorpass-band filter circuit configured to pass frequency components of aninput signal in a pass-band of frequencies received at an input of theBAW resonator pass-band filter circuit to an output of the BAW resonatorpass-band filter circuit; and a first rejection-band series resonatorcoupled in series with the input of the BAW resonator pass-band filtercircuit or in series with the output of the BAW resonator pass-bandfilter circuit, the first rejection-band series resonator having a firstanti-resonant frequency peak in a rejection-band of frequencies that isless than the pass-band of frequencies.
 2. The BAW resonator filter ofclaim 1 wherein the BAW resonator pass-band filter circuit comprises aladder topology, a lattice topology, or a modified lattice topology. 3.The BAW resonator filter of claim 2 wherein the BAW resonator pass-bandfilter circuit comprises a BAW resonator pass-band filter ladder and thefirst rejection-band series resonator is coupled in series with theinput, the BAW resonator filter further comprising: a secondrejection-band series resonator coupled in series with the output, thesecond rejection-band series resonator having a second anti-resonantfrequency peak in the rejection-band of frequencies.
 4. The BAWresonator filter of claim 1 wherein the pass-band of frequencies isabout 5.49 GHz to about 5.835 GHz.
 5. The BAW resonator filter of claim1 wherein the rejection-band of frequencies is about 5.17 GHz to about5.33 GHz.
 6. The BAW resonator filter of claim 3 wherein the first andsecond anti-resonant frequency peaks are in a range between about 5.17GHz and about 5.33 GHz.